The present invention relates to the production of molded products, wherein a mixture which flows under pressure comprising a pulverulent ground material and a reactive two-component binder, in particular a polyurethane binder, is introduced into molds, and reacted therein to form the molded product. It is preferred that recycled plastic material be used as the pulverulent ground material (and, in particular, ground polyurethane foam waste, used components made from polyurethane composite materials, in particular without prior separation of the various composite materials), optionally in combination with inorganic fillers.
The present invention relates in particular to two-component polyurethane binder systems. However, the present invention may also be used with other two-component binder systems.
It has already been proposed in French patent 1,295,213 and U.S. Pat. No. 3,549,472 to reuse ground or comminuted polyurethane foam with a reactive polyurethane mixture as the binder. However, conventional methods for the production of the binder/ground material mixture lead to disruptive polymer formation in the mixing and conveying units. The necessary cleaning operations involve a shut-down of operations and require the use of solvents, which, apart from being questionable in terms of occupational hygiene, also require costly disposal. The proposals of these two references have not met with industrial acceptance, particularly since the stated proposals could achieve only a low recycling rate, i.e. only a small proportion of recycled ground material could be used in the finished part.
The object of the present invention was, on the one hand, to allow the highest possible recycling rate in the finished part and, on the other, to prevent the formation of polymer in the mixing and conveying units so that operations need not be shut down for costly cleaning operations.